Everything was going very well but now the latest batch tastes different. Fermented but not very acidic. Weaker more watery taste, possibly slight alcohol taste?

The long:

I was about to start my 8th batch of Kombucha (1 week primary ferment each) and tasted a sample from the vessel. It tastes very different this time. It has fermented out the sugar (I can’t taste any residual sugars) and has effervescence but not much acidity. In previous batches it was quite tart and had an apple cider like taste. This tasted weaker, more watery, less acidic, possibly slight alcohol taste. The previous batch was also slightly different but not so much to raise questions. Prior to that everything was consistently good and strong. I’m going by taste and have not taken any PH measurements - I should probably get some in the future.

All the ferments have been very active. Bubbles within hours of starting a batch and a constant stream of bubbles the next morning and throughout the ferment. I have been doing small batches and was planning on moving to a larger batch this time but am reluctant to make changes when it tastes so different and I’m unsure what is happening. I have a few theories but really not sure!

* Hot summer temperatures potentially causing yeast to become dominant and reducing bacteria’s ability to acidify. (Located in Australia, Sydney area) Not sure why this would cause a sudden change when it has been hot throughout all previous batches and the taste was strong and tart prior.

* Brewed tea in hot water and then added sugar after (normally I brew tea in hot sugar water). I presumed doing this would mean the tea would steep more efficiently. Not sure why this should be a problem, in fact I would have thought if it made a stronger tea the Kombucha would be quite happy. This is the only difference in my method through all the batches.

* Something else?

Recipe:

My recipe and method is exactly the same for every batch with the exception above (batch 6 & 7 I steeped tea in boiled water then added sugar after steeping instead of steeping the tea in boiled water with sugar.)

Ingredients:

* 1.5L filtered water

* 4 tsp organic loose leaf black tea

* 1/2 cup organic cane sugar

* 1 cup starter liquid from previous batch

Method:

* Boil 750ml water and steep tea

* Cool sweet tea to room temperature over many hours / full day

* Bottle previous batch and mix all the liquid and sediment reserving 1 cup for next batch plus pellicle.

Everything was going so well and so smoothly. The kombucha was tasting great and the fizz was amazing! I was just waiting for my large glass vessel and spigot which has now arrived. For my next batch (#8) I was eagerly looking forward to start making the larger batches but now I’m not sure what to do. I was going to double the recipe (including starter liquid) and then increase the batch size again in the following batches.

What should I do? Anyone have any ideas what is going on? Should I just bottle it and try another small batch or jump in and make the double recipe?

Any help or suggestions welcome. I have my next batch of tea cooling so hopefully I will have some replies soon!

It also sounds to me like the yeast is taking over. But I doubt the sugar is the problem. I'd just toss the SCOBY and use one from a previous batch (or as cerbu noted, let a new one form) to see if that fixes things. In long-running ferments, stuff sometimes gets out of whack and we do our best to understand and fix, but with the over-production of SCOBYs in a long-running kombucha, you might as well just fall back on an older mother.

An update... I went ahead and started batch #8 last week but reserved starter liquid from the top of the vessel to favour the bacteria over the yeast. I will taste it tomorrow and hope it will be back to normal and ready to bottle.

Also I just tasted a bottle from the problematic batch #7. It was flavoured with Raspberries and absolutely all sweetness was fermented out but it was still not tart or acidic. It tasted alcoholic and not pleasant. I think this is probably more evidence that the yeast has become dominant, probably due to the hot weather we have been having, even though it has been consistently hot throughout all the previous batches and I did not have any problems before.

I really hope the next batch will be back to normal or atleast a big improvement. I will let you know how it goes.

I bottled the next batch (#8) today which tasted great again. Back to the normal taste - clean, tart, Apple cider taste.

I think reserving the starter liquid from the top and not stirring up the yeast & sediment probably made the difference. So glad the problem appears to be resolved and hope that it doesn’t occur again.